![Sample our Physical Sciences journals, sign in here to start your FREE access for 14 days]({"type":"image" , "src" : "/sda/110819/TOC-Subject-Sample-2021-Physical-Sciences.jpg"})
Abstract
Pore formation and evolution is a common physical phenomenon observed in food materials during different dehydration processes. This change affects heat and mass transfer process and many quality attributes of dried product. Many mathematical models ranging from emperical to classical models proposed in the literature for predicting porosity during drying of food materials. Classical model is in its infancy as the required materials properties during drying are not avaiable for the material charecterisation. Empirical and semi-empirical models are reasonably well developed in establishing relationships between pore evolution and moisture content and determining experimental based coefficients. However, there are no simplistic models that considered process conditions and material properties together to predict the porosity. The purpose of this work is to develop a simplistic theoretical model for pore formation taking both process parameters and changing material properties during drying into consideration. A new “shrinkage velocity” approach has been introduced and the model has been developed based on this shrinkage velocity taking into account the main factors that influence the porosity including the glass transition temperature. Experimental results show good agreement with simulated results and thus validated the model. This study is expected to enhance the current understanding of pore formation of deformable materials during drying.
Acknowledgement
The authors like to acknowledge the contribution of Dr Chandan Kumar in developing the mathematical formulations and COMSOL solution. This research was conducted at the experimental and analysis facilities of the Queensland University Technology (QUT) - Brisbane, Australia. The authors would also like to acknowledge the contributions of Kim Luong, Andres Orejuela, and Shri Siddharathan in experiments.
Nomenclature
| M | = | Mass Kg |
| V | = | Total Volume m3 |
| W | = | Water content kg of water/kg of sample |
| X | = | Water content kg of water/kg of solid |
| T | = | Temperature K |
| M | = | Molecular weight of water kg/mol |
| a, b, c, d, e, f, j | = | Fitting parameters involved in empirical models |
| Greek symbols | ||
| = | Shrinkage expansion function | |
| = | Porosity | |
| = | Collapse function | |
| = | Density kg/m3 | |
| S | = | Density ratio, volume shrinkage coefficient |
| = | Volume-shrinkage coefficient | |
| Subscripts | ||
| 0 | = | Initial |
| A | = | Air |
| B | = | Bulk |
| S | = | Solid |
| W | = | Water |
| P | = | Particle |
| G | = | Glass transition |
| M | = | Material |